Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the behavioral disclosure burden. It discloses a non-obvious limitation: BFS does not publish rent below canton level except for 10 cities, so results may describe the canton, and it tells the caller that the response identifies which scope applies. This is valuable transparency beyond the schema.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, no filler. The main purpose is front-loaded in the first sentence and the important data-scope caveat occupies the second without redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a low-complexity, two-parameter retrieval tool with no output schema, the description covers the operation, the optional parameter, and the key output nuance (whether the figure is municipal or cantonal). It could optionally state units/currency, but that is a minor gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, including bfsId provenance and rooms examples, so the baseline applies. The description adds only general meaning that rooms are an optional size filter, which is already represented in the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb ('Reports') and identifies a precise resource: the Swiss Federal Statistical Office's average monthly rent for a municipality, with an optional room-size filter. This distinguishes it from sibling tools like listing_search or tax_lookup because it names the official statistical source and the rent metric.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description makes the tool's domain clear and implies it should be used when an official BFS average rent figure is needed. However, it never explicitly states when to prefer this tool over siblings such as listing_search or favorable_municipalities, and gives no exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.